The regulation of photosynthetic membrane (chromatophore) formation in Rhodopseudomonas capsulata will be studied by the methods of biochemical genetics. Carotenoids are an integral component of chromatophores, and the molecular details of the synthesis and regulation will be investigated by assaying carotenoid biosynthetic enzymes under various conditions which affect membrane composition and in various mutants with altered regulatory responses. The coordination between carotenoid and bacteriochlorophyll biosynthesis will be probed by biochemical and genetics analyses of mutants with pleiotropic changes in both systems, and kinetic analyses of regulatory events. The possibility that plasmids are involved in the formation of the photosynthetic apparatus will be explored via nucleic acid hybridization techniques and genetic studies. The gene transfer system of R. capsulata will be studied to determine if it represents an entirely new bacterial genetic exchange mechanism. Gene transfer will be used to map the genes involved in bacterial photosynthesis.